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The diagnosis of shock depends on a combination of key historical features and physical findings in the proper clinical setting. For example, tachycardia and hypotension in an elderly patient with fever, cough, and dyspnea may represent pneumonia with septic shock. Hemorrhagic shock should be suspected in a middle‐aged man with epigastric pain, hematemesis, melena, and hypotension. Hypotension, tachycardia, and an urticarial rash in a victim of a recent bee sting strongly suggest distributive shock secondary to anaphylaxis. Obstructive shock precipitated by a tension pneumothorax should be suspected in a patient with hypotensive trauma who has unilateral decreased breath sounds and tracheal deviation to the opposite side.

Table 7.1 Categories of shock

Type of shock	Disorder	Examples	Comments
Hypovolemic	Decreased intravascular fluid volume	A. External fluid loss Hemorrhage Gastrointestinal losses Renal losses Cutaneous loss B. Internal fluid loss Fractures Intestinal obstruction Hemothorax Hemoperitoneum Third spacing	Hypovolemic shock states, especially hemorrhagic shock, produce flat neck veins, tachycardia, and pallor
Distributive	Increased “pipe” size: peripheral vasodilation	A. Drug or toxin induced B. Spinal cord injury C. Sepsis D. Anaphylaxis E. Hypoxia/anoxia	Distributive shock states usually show flat neck veins, tachycardia, and pallor. Neurogenic shock due to a cervical spinal cord injury tends to show flat neck veins, normal or low pulse rate, and pink skin
Obstruction	Pipe obstruction	A. Pulmonary embolism B. Tension pneumothorax C. Cardiac tamponade D. Severe aortic stenosis E. Venocaval obstruction	Obstructive shock states tend to produce jugular venous distension, tachycardia, and cyanosis
Cardiogenic	“Pump” problems	A. Myocardial infarction B. Arrhythmias C. Cardiomyopathy D. Acute valvular incompetence E. Myocardial contusion F. Myocardial infarction G. Cardiotoxic drugs/poisons	Cardiogenic shock states tend to produce jugular venous distension, tachycardia, and cyanosis

An important problem in the prehospital diagnosis of shock is the frequent inaccuracy of field assessment. For example, in one analysis, emergency medical technicians (EMTs) made vital sign errors more than 20% of the time [6]. Subsequently, when critical medical decisions are based on the data gathered in the field, multiple assessments should be performed.

EMS clinicians should look for the signs and symptoms of system‐wide reduction in tissue perfusion, such as tachycardia, tachypnea, mental status changes, and cool, clammy skin (Box 7.1). When available, adjunctive technologies can provide improved recognition and assessment of shock by revealing reductions in expired CO₂, hypovolemia, obstruction or poor cardiac contractility, and elevated serum lactate levels.

Vital signs that fall outside of expected ranges must be correlated with the overall clinical presentation. Vital signs have a broad range of normal values. They must be interpreted in the context of the individual patient. A petite 45‐kg, 16‐year‐old girl with lower abdominal pain with a reported blood pressure of 88 mmHg systolic by palpation may have a ruptured ectopic pregnancy, or may just be at her baseline blood pressure. An elderly patient with significant epistaxis may be hypertensive due to catecholamine release and vasoconstriction despite being relatively volume depleted. Consideration should be given to patient age, comorbid conditions, and medications that may affect the interpretation of vital signs.